Composition for partitioning blood components

ABSTRACT

A blood-partitioning composition comprising a mixture of 
     (1) a thixotropy-imparting agent, 
     (2) a first viscous liquid material having strong interaction with the thixotropy-imparting agent, and 
     (3) a second viscous liquid material having no strong interaction with the thixotropy-imparting agent and having good compatibility with the first viscous liquid material, 
     said composition having a specific gravity at 20° C. of from 1.03 to 1.08, and use of the composition in a method for partitioning a sample of blood.

This is a division of application Ser. No. 292,029, filed Aug. 11, 1981,now U.S. Pat. No. 4,457,782.

This invention relates to a composition for partitioning bloodcomponents, and more specifically to a novel composition for separatinga relatively light normally liquid blood phase containing serum orplasma from a relatively heavy normally solid blood phase containingerythrocytes, leukocytes, platelets, etc. by subjecting a sample ofblood to centrifugation.

In recent years, diagnostic testing of blood components in clinicallaboratories has become very important and the number of cases subjectedto such testing has been increasing. Many of biochemical tests involveuse of blood serum or plasma as a sample, and as a preparatory procedurefor examination, it is necessary to separate blood serum or plasma fromsolid blood components such as erythrocytes and leukocytes. It is theconventional practice to sample blood serum or plasma by centrifugingwhole blood thereby to sediment a blood cell portion, and siphoning thesupernatant liquid by a pipette. This method, however, results ininsufficient separation of the serum or plasma portion and is verytime-consuming. Various methods have therefore been suggested recentlyto perform this separating operation with simplicity in high yields.

One of such prior methods suggested comprises adding to a sample ofblood a substance having a specific gravity intermediate between serumor plasma and a solid blood component, and positioning this substanceintermediate between the two types of blood components by centrifugationthereby forming a partitioning wall between them. Although this methodenables serum or plasma to be separated only by decantation and permitssaving of both time and labor, it is not without defects.

Such partitioning wall-forming materials so far proposed are availablein the form of a solid, a liquid or a mixture of these (see, forexample, U.S. Pat. Nos. 3,780,935 and 3,852,194).

Solid materials include, for example, a powdery or pelletized materialof polystyrene. When this material is used, its function as apartitioning wall is insufficient, and the blood cells may get mixedwith the serum or plasma. Or the partitioning wall itself is susceptibleto destruction.

Acrylic polymers are known as the liquid partition-forming material.Production of a highly viscous liquid polymer, such as the acrylicpolymers, from monomers generally gives rise to difficult problems suchas the removal of impurities depending upon the control of the reactionand the method of performing the reaction. In addition, the liquidmaterial has the defect of poor adaptability for transportation andstorage before use because it has flowability.

Known solid-liquid mixtures include thixotropic compositions such as amixture of a silicone and silica powder and a mixture of modified liquidpolybutadiene and alumina. They have the defect that their viscositygenerally increases or decreases with the lapse of time. When theviscosity of such a composition increases, a strong centrifugal force isrequired for a long period of time for moving the composition to anintermediate position between the serum or plasma and a blood cellportion by centrifugation after it has been stored for a long period oftime in the bottom of a container. Sometimes, such a composition doesnot become flowable even when subjected to a centrifugal force of 500 to2,000 G which is usually employed in hospital and biomedicallaboratories. Conversely, when the viscosity of the compositiondecreases with time, the composition has a decreased viscosity afterstorage for a long time in a container. If the stored composition iscentrifuged together with a sample of blood in a container and thecontainer is inclined for pouring off the serum, the partitioning wallof the composition will collapse and the blood cells will get mixed withthe serum.

It is an object of this invention therefore to provide a composition forpartitioning a sample of blood, which is free from the aforesaid defectsand does not substantially change in viscosity with the lapse of time.

Another object of this invention is to provide a composition forpartitioning a sample of blood, which can easily form a stablepartitioning wall under normal centrifuging conditions and permits verysimple and accurate separation of the serum or plasma portion.

Still another object of this invention is to provide a composition forpartitioning a sample of blood, which can be transported and storedsimply without any particular attention or device.

A further object of this invention is to provide use of suchpartitioning composition for the partitioning of a sample of blood.

Other objects and advantages of this invention will become apparent fromthe following description.

According to this invention, there is provided a composition forpartitioning a sample of blood, said composition comprises a mixture of

(1) a thixotropy-imparting agent,

(2) a first viscous liquid material having strong interaction with thethixotropy-imparting agent, and

(3) a second viscous liquid material having no strong interaction withthe thixotropy-imparting agent and having good compatibility with thefirst viscous liquid material,

said composition having a specific gravity at 20° C. of from 1.03 to1.08.

The blood partitioning composition provided by this invention will nowbe described in detail.

Thixotropy-imparting agent

Since the composition of this invention serves to form a partitioningwall in an interface between the serum or plasma phase and the solidphase (including erythrocytes, leukocytes, platelets, etc.) separated bycentrifugation, it is necessary to stabilize the partitioning wall inorder to avoid re-mixing of the serum or plasma with the solidcomponents after separation. For example, the partitioning wall must bestabilized against flowing and collapsing during transportation of acontainer containing the composition of this invention and a sample ofblood after the separating operation, or during inclining of thecontainer for separation of the serum or plasma. It is for this purposethat the thixotropy-imparting agent is used.

In the present specification and the appended claims, the term"thixotropy-imparting agent" denotes a solid powder, particularly aninorganic solid powder, which can impart thixotropy to a mixture of thefirst and second viscous liquid materials.

Such a solid powder has an average particle diameter of generally 1 to1,000 millimicrons, preferably 1 to 100 millimicrons, especiallypreferably 5 to 30 millimicrons, a specific surface area of generally atleast 10 m² /g, preferably 50 to 500 m² /g, especially preferably 100 to400 m² /g, and a specific gravity of generally 1.5 to 30, preferably 1.8to 2.5, and most suitably 2.0 to 2.4. Desirably, the solid powder issubstantially insoluble in water.

Examples of the inorganic solid powder capable of imparting thixotropyin accordance with this invention include powders of silica, alumina,glass, talc, kaolin, bentonite, titania, zirconium, asbestos and carbonblack.

If desired, these solid powders may be subjected to a surfacehydrophilizing or hydrophobizing treatment, for example a graftingreaction using a grafting agent such as a combination of a vinylsilanecompound and a vinyl monomer, or a coupling reaction using a couplingagent such as a silane coupling agent (e.g.,γ-chloropropyltrimethoxysilane or γ-glycidoxypropyltrimethoxysilane).

These solid powders may be used singly or as a mixture of two or more.

Among these thixotropy-imparting agents, fine silica powder is mostsuitable in this invention. The fine silica powder may, if desired, behydrophobized at its surface by coupling reaction withdimethyldichlorosilane.

First viscous liquid material

The first viscous liquid material used to prepare the composition ofthis invention by mixing with the thixotropy-imparting agent is aviscous liquid material having strong interaction with thethixotropy-imparting agent.

The expression "having strong interaction with the thixotropy-impartingagent", as used in the present specification and the appended claims,means that when a certain thixotropy-imparting agent and a certainviscous liquid material are mixed and dispersed uniformly and thencentrifuged for 30 minutes at a rotating speed of 4,000 rpm by acentrifugal separator having an arm length of 10 cm, no localization isseen in the distribution of the components of the above mixture. Thelocalization of the distribution is evaluated in the following manner.Specifically, analysis samples are collected at several different pointsof the mixed mass after the centrifugal separation, and weighed. Then,the thixotropy-imparting agent dispersed in the samples is separated andweighed to determine the amount of the thixotropy-imparting agent perunit of the samples. When the differences in the amount of thethixotropy-imparting agent among the samples is within ±20%, it isjudged that there is no localization in the distribution.

The first viscous liquid material having strong interaction with thethixotropy-imparting agent (inorganic solid powder) may generally be asubstantially a water-in-soluble natural material or a syntheticpolymeric material which is liquid at room temperature (about 5° toabout 30° C.) and contains a hydrophilic functional group in themolecule, particularly a carbonyl group (which may be present in theform of a carboxyl group, an ester linkage, an amide linkage and/or aketone linkage), or an epoxy group. The amount of the carbonyl groups orepoxy groups is not critical, and can be varied depending upon the typeof the thixotropy-imparting agent to be mixed, for example. The carbonylgroups can exist in a carbonyl equivalent of generally 80 to 300,preferably 100 to 200, and the epoxy groups can exist in an epoxyequivalent of generally 100 to 1,000, preferably 200 to 500. The"carbonyl equivalent" and "epoxy equivalent" respectively mean thenumber of grams of a resin containing 1 gram-equivalent of carbonyl orepoxy groups.

Specific examples of the first viscous liquid material are given below.

(1) Acrylic oligomers such as homo- or copolymers of a low degree ofpolymerization having a number average molecular weight of 500 to 10,000derived from acrylic acid esters, methacrylic acid esters, maleic acidesters, etc.

(2) Polyester oligomers such as a copolymer of a dicarboxylic acid and adiol which has a number average molecular weight of 500 to 10,000.

(3) Acid-modified liquid synthetic polymeric materials, such as amaleinized product of a liquid rubbery polymer such as liquidpolybutadiene and liquid polyisoprene, which has a number averagemolecular weight of 500 to 10,000.

(4) Animal and vegetable oils, such as soybean oil, linseed oil,safflower oil, and fish oils.

(5) Liquid epoxy resins, such as a condensation product of bisphenol Aand epichlorohydrin, which have an epoxy equivalent of 150 to 500 and amolecular weight of 300 to 500.

(6) Epoxy-modified liquid synthetic polymeric materials, such as anepoxidized product of liquid 1,2-polybutadiene or liquid1,4-polybutadiene which has an epoxy equivalent of 150 to 1,000 and anumber average molecular weight of 1,000 to 5,000.

(7) Epoxy-modified products of animal and vegetable oils such asepoxidized soybean oil, epoxidized linseed oil and epoxidized saffloweroil.

Among these first viscous liquid materials, the epoxy-modified liquidsynthetic polymeric materials and epoxidized animal and vegetable oilsare especially preferred.

The first viscous liquid material used in this invention is a liquidepoxidized animal or vegetable oil or a synthetic polymeric materialcontaining carbonyl or epoxy groups, said liquid being viscous at roomtemperature, and desirably has a viscosity, measured at 20° C., ofgenerally at least 200 cps, preferably 300 to 30,000 cps, morepreferably 350 to 10,000 cps. Conveniently, it has a specific gravity at20° C. of generally 0.9 to 1.2, preferably 1.0 to 1.1, more preferably1.02 to 1.08.

Examples of the first viscous liquid material which can be especiallyadvantageously used in this invention are epoxidized soybean oil havinga viscosity at 20° C. of 300 to 700 cps and a specific gravity of 20° C.of 0.95 to 1.00, and epoxidized products of liquid 1,2-polybutadiene andliquid 1,4-polybutadiene which have an epoxy equivalent of 150 to 250and a number average molecular weight of 3,000 to 5,000.

Second viscous liquid materials

The second viscous liquid material used in combination with the firstviscous liquid material in accordance with this invention is a viscousliquid material having no strong interaction with thethixotropy-imparting agent. Thus, the second viscous liquid material issuch that when it is mixed with the thixotropy-imparting agent anduniformly dispersed and centrifuged for 30 minutes at a rotating speedof 4,000 rpm by a centrifugal separator having an arm length of 10 cm,localization occurs in the distribution of the thixotropy-impartingagent in the mixture.

Although the second viscous liquid material has no strong interactionwith the thixotropy-imparting agent to be mixed, it should have goodcompatibility with the first viscous liquid material.

In the present specification and appended claims, the expression that"the second viscous material has good compatibility with the firstviscous liquid material" means that when the first viscous liquidmaterial and the second viscous liquid material are uniformly mixed andthe mixture was allowed to stand for 1 week at room temperature, nophase separation perceptible to the naked dye occurs.

The second viscous liquid material having the above properties is ahigh-molecular-weight material which is composed substantially only ofcarbon and hydrogen and is liquid at room temperature, and ahigh-molecular-weight material which is composed substantially ofcarbon, hydrogen and chlorine and is liquid at room temperature.Specific examples are given below.

(1) Liquid chlorinated paraffins which have a number average molecularweight of 300 to 600 and a chlorine content of 5 to 40% by weight.

(2) Liquid polyolefins, for example polybutene having a number averagemolecular weight of 300 to 1,500 polyisoprene having a number averagemolecular weight of 10,000 to 50,000, and polybutadiene having a numberaverage molecular weight of 1,000 to 3,000. These polyolefins maycontain hydroxyl, epoxy or carbonyl groups at the ends in order toincrease their compatibility with the first viscous liquid material.

(3) Chlorinated products of the materials described in (2) above. Thesechlorinated products desirably have a chlorine content of generally 5 to40% by weight, preferably 7 to 20% by weight. A chlorinated product ofpolybutene having a number average molecular weight of 600 and achlorine content of 20% by weight is preferred.

These materials may be used singly or as a mixture of two or more.

Advantageously, the above second viscous liquid materials used inaccordance with this invention which are viscous at room temperature andhave a viscosity measured at 20° C. of at least 1,000 cps, preferably6,000 to 150,000 cps, more preferably 10,000 to 30,000 cps. Desirably,they have a specific gravity at 20° C. of generally 0.85 to 1.20,preferably 0.95 to 1.10, more preferably 1.00 to 1.08.

Especially advantageously used as the second viscous liquid material inthis invention is chlorinated polybutene having a number averagemolecular weight of 400 to 1,500 having a chlorine content of 7 to 20%by weight.

Water-insoluble amines

The composition of this invention comprising a mixture of the aforesaidthixotropy-imparting agent, first viscous liquid material and secondviscous liquid material may, if desired, further contain a substantiallywater-insoluble amine. Inclusion of the amine can lead to a markedimprovement in the stability of the viscosity of the composition withthe lapse of time. The expression "substantially water-insoluble" meansthat the solubility in water is not more than 0.1% at 20° C.

The substantially water-insoluble amine used for the above purpose isconveniently compatible with the first or second viscous liquidmaterial, and has a molecular weight of generally 100 to 500, preferably150 to 400. Especially suitable amines are of the following generalformula ##STR1## wherein R₁, R₂ and R₃ each represent a hydrogen atom oran alkyl group, provided that at least one of R₁, R₂ and R₃ is a higheralkyl group having at least 8 carbon atoms, preferably 12 to 20 carbonatoms, which alkyl group may be mono-substituted with a polyoxyalkylenegroup such as a polyoxyethylene or polyoxypropylene group. Specificexamples of the amine are dodecylamine, tetradecylamine, hexadecylamine,octadecylamine, dodecyldimethylamine, tetradecyldimethylamine,octadecyldimethylamine, polyoxyethyleneoctadecylamine, andtrioctylamine.

These amines may be used singly or as a mixture of two or more.

Among the above amines, octadecyldimethylamine and trioctylamine areespecially suitable.

Other additives

The composition in accordance with this invention may, if desired,further contain substantially water-insoluble coloring agents, titaniumoxide and zinc oxide, etc. in addition to the aforesaid components.

Preparation of the composition of this invention

The composition of this invention can be prepared by intimately mixingthe individual components described hereinabove. The order of additionof these components is not at all restricted. For example, all of thecomponents may be mixed simultaneously. Or the mixing may be performedin a multiplicity of steps. For example, two selected components arefirst mixed, and then the remaining components are added and mixedeither sequentially or at once; or vice versa. Generally, it isconvenient to first mix the first viscous liquid material and the secondviscous liquid material, and then simultaneously, or successively in anoptional order, mix the thixotropy-imparting agent and if desired, thewater-insoluble amine and other additives.

The proportions of the individual components vary depending upon thetypes of the thixotropy-imparting agent, the first viscous liquidmaterial and/or second viscous liquid material, etc. Generally, thethixotropy-imparting agent can be used in an amount of 2 to 30 parts byweight, preferably 3 to 15 parts by weight, more preferably 4 to 8 partsby weight, per 100 parts by weight of the first and second viscousliquid materials combined. The ratio between the first viscous liquidmaterial and the second viscous liquid material varies depending uponthe degree of interaction between each of these viscous liquid materialsand the thixotropy-imparting agent. Generally, it is convenient to use20 to 600 parts by weight, preferably 30 to 500 parts by weight, morepreferably 50 to 450 parts by weight, of the second viscous liquidmaterial per 100 parts by weight of the first viscous liquid material.

The amount of the water-insoluble amine to be used optionally is neitherrestricted strictly, and can be varied depending upon the types of theother components, etc. Generally, the suitable amount of thewater-insoluble amine is 0.001 to 0.1 part by weight, preferably 0.005to 0.09 part by weight, more preferably 0.01 to 0.05 part by weight, perpart by weight of the thixotropy-imparting agent. The amounts of theother additives are small depending upon their types, and are usuallynot more than 5.0% by weight based on the weight of the entirecomposition.

Since the composition in accordance with this invention is used to forma partitioning wall between the serum or plasma phase and the solidblood phase by a centrifugal action, it should have a specific gravityintermediate between the two phases. Thus, the composition should have aspecific gravity in a standard condition at 20° C. of 1.03 to 1.08,preferably 1.04 to 1.06.

Accordingly, in preparing the composition of this invention, the mixingproportions of the individual components should be selected within theabove range such that the specific gravity of the resulting compositionat 20° C. comes within the aforesaid range.

The mixing of the individual components can be performed in a customarymanner by using a mixing device, such as a three-roll mill or aplanetary mixer, generally at room temperature and in some cases at anelevated temperature of up to about 100° C.

The composition of this invention prepared as above is a thixotropiccomposition having a specific gravity at 20° C. of 1.03 to 1.08,preferably 1.04 to 1.06, a viscosity at a shear speed of 1 sec⁻¹ of60,000 to 400,000 cps, preferably 100,000 to 250,000 cps, and athixotropy coefficient of generally at least 1.8, preferably 2.0 to 4.0.

The term "thixotropy coefficient", as used herein, denotes a valuecalculated in accordance with the following equation. ##EQU1##

The composition of this invention for partitioning of a sample of bloodhas such moderate thixotropy and shows no increase in viscosity withtime as is demonstrated by working examples given hereinbelow. Hence,not only immediately after production but also after storage for longperiods of time, no specially strong centrifugal force is required, buta partitioning wall of the composition is formed easily within a bloodcollection tube under normal centrifuging conditions (at a rotatingspeed of 1,500 to 3,500 rpm) so that serum or plasma can be separatedwith simplicity and good accuracy. Furthermore, since the viscosity ofthe composition of this invention does not decrease with time, it canstably form a partitioning wall even when used after storage for a longperiod of time. Once the partitioning wall has been formed, it will notcollapse even when after the lapse of a long period of time, the blooddrawing tube is inclined. In this way, the composition of this inventionhas many advantages over conventional products used for the samepurpose.

In separating the blood components by using the composition of thisinvention, no particular attention should be paid, and any known method(for example, the method described in the above-cited U.S. Patentspecifications) can be used. For example, a certain fixed amount of thecomposition of this invention is put in a container, and a sample ofblood drawn from the subject is added. The mixture is then centrifugedfor about 2 to about 20 minutes at a rotating speed of 1,500 to 3,500rpm. As a result, a partitioning wall of the composition of thisinvention is formed in the interface between the serum or plasma and thesolid phase containing erythrocytes, etc. Thus, the serum or plasma canbe separated and taken out simply with good accuracy by such anoperation as decantation.

The following Examples further illustrate the present invention.

The specific gravities, viscosities, specific surface areas andthixotropy coefficients used in these examples are all measured at 20°C. The viscosities are measured at a shearing speed of 1 sec⁻¹.

EXAMPLE 1

(A) Silica powder having an average particle diameter of 10millimicrons, a specific surface area of 200 m² /g and a specificgravity of 2.2 as a thixotropy-imparting agent, epoxidized soybean oilhaving a specific gravity of 1.00, a viscosity of 420 cps and an epoxyequivalent of 200 as a first viscous liquid material and liquidchlorinated polybutene having a specific gravity of 1.00, a viscosity of8,000 cps and a chlorine content of 14% by weight as a second viscousliquid material were provided.

(B) Using these components, the three mixtures shown in Table 1 eachconsisting of two components were prepared. The mixtures a and b wereeach put in a glass container and centrifuged at a rotating speed of4,000 rpm for 30 minutes using a centrifugal separator having an armlength of 10 cm. Immediately after the centrifugation, the tube wasmaintained perpendicular, and the state of the mixture therein wasobserved.

                  TABLE 1                                                         ______________________________________                                                            Epoxidized                                                       Silica powder                                                                              soybean oil                                                                             Liquid chlorinated                                     (parts by    (parts by polybutene                                      Mixture                                                                              weight)      weight)   (parts by weight)                               ______________________________________                                        a      1            10        --                                              b      1            --        10                                              c      --            3         2                                              ______________________________________                                    

In the mixture a, silica was uniformly dispersed in the epoxidizedsoybean oil, but silica in the mixture b was localized below the liquidchlorinated polybutadiene. On the other hand, when the mixture c wasallowed to stand at room temperature for 1 week in a container. It wasfound that the epoxidized soybean oil and the liquid chlorinatedpolybutene were uniformly dissolved in each other, and no phaseseparation occurred.

(C) The silica powder, epoxidized soybeans oil and the liquidchlorinated polybutene in this order were weighed in a weight ratio of1:3:7. In a vacuum vessel kept at 50° C., the epoxidized soybean oil andthe liquid chlorinated polybutene were mixed with stirring, the silicapowder was added and dispersed uniformly. The mixture was cooled to 20°C. to give a blood partitioning composition having a specific gravity of1.05. The composition had a viscosity at 1 sec⁻¹ of 200,000 centipoisesand a thixotropy coefficient of 3.0.

One gram of the composition was introduced into each of four 10 ml glasstubes. Immediately after production, a sample of blood was added to oneof these tubes, and centrifuged at a rotating speed of 2,000 rpm for 3minutes with an arm length of 10 cm. The composition formed apartitioning wall between the serum and the blood clot, and the serumcould be easily separated and collected by decantation.

Another tube was turned upside down, and inclined at an angle of about60 degrees to the horizontal plane. However, the composition in it didnot flow.

The remaining two tubes were left to stand at room temperature, andafter one month, subjected to the same tests as above. There was noincrease or decrease in the viscosity of the composition, and the sametest results as above were obtained.

The tube in which the partitioning wall was formed as a result ofcentrifugal separation effected immediately after the production of thecomposition was again inclined, but the partitioning wall did notcollapse.

COMPARATIVE EXAMPLE 1

The same silica powder, epoxidized soybean oil and liquid chlorinatedpolybutene as used in Example 1 were provided.

One part by weight of the silica powder was added to 10 parts by weightof the epoxidized soybean oil, and the mixture was heated with stirringto form a mixture d having a specific gravity of 1.05. Separately, 1part by weight of the silica powder was added to 6 parts by weight ofthe liquid chlorinated polybutene, and the mixture was heated withstirring to give a mixture e having a specific gravity of 1.05.

A sample of blood was added to the mixture d in a tube, and centrifugedunder the same conditions as in Example 1. Immediately after theproduction of the mixture d, a partitioning wall of the mixture wasformed in an intermediate position in the whole blood. One month later,its viscosity became so high that the composition became immovable andno partitioning wall was formed.

The mixture e was subjected to the same inverting test as in Example 1.Both immediately after the production and after one month from then, themixture e was seen to flow downward slowly.

EXAMPLE 2

Amorphous hydrophilic silica powder having a specific gravity of 2.2, aspecific surface area of 200 m² /g and an average particle diameter of10 millimicrons as a thixotropy-imparting agent, epoxidized soybean oilhaving a specific gravity of 1.0, a viscosity of 1,700 cps and an epxoyequivalent of 200 as a first viscous liquid material, and liquidchlorinated polybutene having a specific gravity of 1.05, a viscosity of50,000 cps and a chlorine content of 20% by weight as a second viscousliquid material were provided.

The fine silica powder, epoxidized soybean oil and liquid chlorinatedpolybutene were weighed in a weight ratio of 1:8:2 in this order, and ina vacuum vessel at 50° C., the epoxidized soybean oil and the liquidchlorinated polybutene were mixed with stirring, and then the finesilica powder was added and dispersed uniformly to give a bloodpartitioning composition having a specific gravity of 1.06. The mixturehad a viscosity of 1 sec⁻¹ of 150,000 centipoises and a thixotropycoefficient of 2.5.

One gram of the composition was introduced into each of 10 ml glasstubes. Immediately after preparation of the composition, a sample ofblood was added to one of these tubes, and after coagulation of theblood, centrifuged at a rotating speed of 2,500 rpm for 3 minutes withan arm length of 10 cm. As a result, the composition formed apartitioning wall between the serum and the blood cell portion, and theserum could be easily separated and collected by decantation.

Samples of blood withdrawn from subjects were biochemicaly tested for 32items including proteins, lipids, serum enzymes, inorganic ions, etc. inthe absence or presence of the resulting composition as a serumseparating material. The serum test values were then compared.Substantially the same results were obtained, and the use of this serumseparating material does not at all affect the serum test values.

On the other hand, another tube containing the composition alone wasturned upside down, and inclined at an angle of about 60° with respectto the horizontal plate. However, the composition did not flow.

Furthermore, the composition was stored at room temperature for 30 days,and then subjected to the same biochemical tests and inverting test asabove. The results were the same. Specifically, there was no increase ordecrease in the viscosity of the composition, and a partitioning wall ofthe composition was formed easily. The results of biochemical testing ofthe serum appeared to be the same as those obtained by using thecomposition immediately after its preparation. The serum separatingcomposition did not flow even when the tube was inverted at 60°.

The tube in which the partitioning wall was formed as a result of thecentrifugal separation effected immediately after the preparation of theabove composition was again inclined 30 days later. But the partitioningwall did not collapse.

COMPARATIVE EXAMPLE 2

One part by weight of the same fine silica powder as used in Example 2and 9 parts by weight of 2-ethylhexyl acrylate oligomer having aspecific viscosity of 1.0 and a viscosity of 100,000 were mixeduniformly to give a composition. Samples of the serum were obtainedunder the same conditions as in Example 2 using the compositionimmediately after production as a serum separating agent, and werebiochemically tested for the same items as in Example 2. The resultswere compared with the serum test values of samples of serum collectedby centrifuging the blood without using the aforesaid separating agentand collecting the serum by a pipette. Clear differences were seen intwo items regarding proteins and two items regarding lipid.

The composition was stored at room temperature for 30 minutes, and thenintroduced into a glass tube. Furthermore, a sample of blood was addedand centrifuged at a rotating speed of 2,500 rpm using a centrifugalseparator having an arm length of 10 cm. However, the composition didnot move, and in order to form a partitioning wall intermediate betweenthe serum and the blood cell portion, a period of 10 minutes at 4,000rpm was required.

EXAMPLE 3

Nine parts by weight of silica powder having an average particlediameter of 10 millimicrons, a specific surface area of 200 m² /g and aspecific gravity of 2.2 as a thixotropy-imparting agent, 70 parts byweight of liquid chlorinated polybutene having a specific gravity of1.02 and a viscosity of 1,000 cps as a second liquid viscous liquidmaterial, 21 parts by weight of epoxidized soybean oil having a specificgravity of 1.0, a viscosity of 1,700 cps and an epoxy equivalent of 200as a first viscous liquid material, and 0.2 part by weight of octylaminewere kneaded on a three-roll mill to give a blood partitioningcomposition having a specific gravity of 1.06. The composition had aviscosity at 1 sec⁻¹ of 180,000 and a thixotropy coefficient of 2.0.

The composition was then introduced in an amount of 1 g into a 10 mlglass tube. A sample of blood was added, and after the coagulation ofthe blood, centrifuged for 3 minutes at a rotating speed of 2,500 rpm(1160 G). The composition formed a partitioning wall intermediatebetween the serum and blood clot. The tube was inclined in order toseparate the serum. The serum could be collected without collapsing ofthe partitioning wall. The same inverting test as in Example 1 wascarried out, but the composition did not flow.

Furthermore, the composition was stored at 40° C. for 30 days, and thesame test as above was carried out. No effect on the formation of thepartitioning wall was noted, and in the inverting test, the compositiondid not flow. Thus, the composition was found to have very goodstability with time.

EXAMPLE 4

Six parts by weight of silica powder having a particle diameter of 16millimicrons, a specific surface area of 130 m² /g and a specificgravity of 2.2 as a thixotropy-imparting agent, 17 parts of epoxidizedsoybean oil having a specific gravity of 1.00 and a viscosity of 410 cpsas a first viscous liquid material, 77 parts of a second viscous liquidchlorinated polybutene having a specific viscosity of 1.02 and aviscosity of 9,000 cps as a second viscous liquid material, and 0.2 partby weight of octadecyldimethylamine were kneaded on a three-roll mill togive a blood partitioning composition having a specific gravity of 1.05,a viscosity of 150,000 cps and a thixotropy coefficient of 2.2.

One gram of the composition was poured into each of 10 ml glass tubes.Then, a sample of blood was added, and after coagulation of the blood,was centrifuged at a rotating speed of 2,500 rpm for 10 minutes with armlength of 10 cm. As a result, a partitioning wall was formedintermediate between the serum and the blood cell portion. The serumcould be easily separated and collected by decantation.

Samples of blood withdrawn from subjects were biochemically tested for32 items including proteins, lipids, serum enzymes, inorganic ions, etc.in the absence or presence of the resulting composition as a serumpartitioning agent. The serum test valves were then compared, andsubstantially the same results were obtained. The use of this serumseparating agent did not affect the serum test values.

On the other hand, a glas tube containing this serum separating agentwas turned upside down and inclined at an angle to 60° with respect tothe horizontal plane. The composition did not flow. When the compositionwas stored at 40° C. for 2 months and then subjected to the same test asabove, quite the same results were obtained. Specifically, a stablepartitioning wall was formed by centrifugation at 2,500 rpm for 10minutes. There was no effect on the serum test values, and thecomposition did not flow in the inverting test.

EXAMPLE 5

Four parts by weight of silica powder having an average particlediameter of 7 millimicrons, a specific surface area of 300 m² /g and aspecific gravity of 2.2 as a thixotropy-imparting agent, 80 parts byweight of polybutyl acrylate oligomer having a specific gravity of 1.0and a viscosity of 8,000 centipoises as a first viscous liquid material,16 parts by weight of liquid chloroprene having a specific gravity of1.20 and a viscosity of 50,000 cps as a second viscous liquid material,and 0.5 part of trioctylamine were kneaded by a planetary mixer to givea blood partitioning composition having a specific gravity of 1.05 and aviscosity of 200,000 cps and a thixotropy coefficient of 2.0. Thiscomposition had the equivalent performances to the composition obtainedin Example 4, and showed quite the same performances after it was storedfor 2 months at 40° C.

EXAMPLE 6

Five parts by weight of hydrophobic silica powder having an averageparticle diameter of 16 millimicrons, a specific surface area of 110 m²/g and a specific gravity of 2.2 as a thixotropy-imparting agent, 25parts by weight of epoxidized 1,2-polybutadiene having a specificgravity of 0.99 and a viscosity of 50,000 cps as a second viscous liquidmaterial, 70 parts by weight of chlorinate polybutene having a specificgravity of 1.05 and a viscosity of 30,000 cps as a second viscous liquidmaterial, and 0.1 part by weight of dodecyldimethylamine were kneaded bya planetary mixer to give a blood partitioning composition having aspecific gravity of 1.06, a viscosity of 160,000 cps and a thixotropycoefficient of 2.1. The composition had the same performance as inExample 4.

EXAMPLE 7

Five parts by weight of hydrophobic silica powder having a particlediameter of 16 microns, a specific surface area of 110 m² /g and aspecific gravity of 2.2 as a thixotropy-imparting agent, 30 parts byweight of a 50:50 mixture (viscosity 4,500 cps; specific gravity 1.0) ofepoxidized soybean oil having a viscosity of 410 cps and a specificgravity of 1.0 and polybutyl acrylate oligomer having a viscosity of8,000 cps and a specific gravity of 1.0 as a first viscous liquidmaterial, 65 parts by weight of chlorinated polybutene having aviscosity of 23,000 cps and a specific viscosity of 1.03 as a secondviscous liquid substance and 0.5 part of triocytlamine were kneaded on athree-roll mill to give a blood-partitioning composition having aspecific gravity of 1.05, a viscosity of 150,000 cps and a thixotropycoefficient of 2.3. The composition had the same performances as inExample 4.

What we claim is:
 1. A blood-partitioning composition consistingessentially of a mixture of(1) a thixotropy-imparting agent which is aninorganic solid powder having an average particle diameter of from 1 to1,000 millimicrons, a specific surface area of at least 10 m² /g and aspecific gravity in the range of from 1.5 to 3.0; (2) a first viscousliquid material having strong interaction with the thixotropy-impartingagent such that when the thixotropy-imparting agent is uniformlydispersed with the first viscous liquid and then centrifuged, nolocalization of said thixotropic agent occurs in the centrifuged liquid,said first viscous liquid having a viscosity at 20° C. of at least 200centripoises and a specific gravity at 20° of from 0.9 to 1.2, saidfirst material being a natural animal or vegetable oil modified withepoxy groups or a synthetic polymeric material containing carbonyl orepoxy groups in the molecule, and wherein said first material is liquidat room temperature; (3) a second viscous liquid material having nostrong interaction with the thixotropy-imparting agent such that whenthe thixotropy-imparting agent is uniformly dispersed with the secondviscous liquid material and then centrifuged, the thixotropy-impartingagent is localized in said second viscous liquid, said second viscousliquid having good compatibility with the first viscous liquid materialsuch that no substantial phase separation occurs upon mixing the twoliquids, said second liquid material having a viscosity at 20° C. of atleast 1,000 centipoises and a specific gravity at 20° C. of 0.85 to 1.20and being a high-molecular-weight material liquid at room temperaturecomposed substantially only of carbon and hydrogen or ahigh-molecular-weight material liquid at room temperature composedsubstantially of carbon, hydrogen and chlorine; and (4) (a) at least onewater-insoluble amine(;) of the following formula: ##STR2## wherein R₁,R₂ and R₃ each represent a hydrogen atom or an alkyl group, providedthat at least one of R₁, R₂ and R₃ is a higher alkyl group containing atleast 8 carbon atoms, which alkyl group may be substituted with onepolyoxyalkylene group;said composition having a specific gravity at 20°C. of from 1.03 to 1.08, a viscosity at a shearing speed of 1 sec⁻¹ offrom 60,000 to 400,000 centipoises and a thixotropy coefficient of atleast 1.8, the amount of said thixotropy-imparting agent being from 2 to30 parts by weight per 100 parts by the combined weight of the first andsecond viscous liquid material, and the amount of said second viscousliquid material being from 20 to 600 parts by weight per 100 parts byweight of the first viscous liquid material.
 2. The composition of claim1 wherein the water-insoluble amine is selected from the groupconsisting of dodecylamine, tetradecylamine, hexadecylamine,octadecylamine, dodecyldimethylamine, tetradecyldimethylamine,octadecyldimethylamine, polyoxyethyleneoctadecylamine and trioctylamine.3. The composition of claim 1 wherein the amount of the water-insolubleamine is from 0.001 to 0.1 part by weight per part by weight of thethixotropy-imparting agent.
 4. The composition of claim 1 wherein saidfirst viscous liquid material is epoxidized soybean oil.
 5. Thecomposition of claim 1 wherein at least one of R₁, R₂ and R₃ is a higheralkyl group containing at 12 to 20 carbon atoms.
 6. The composition ofclaim 1, wherein the amine has a molecular weight of 100 to 500.